Compressor unloader



1935- R. c. M ALLISTER COMPRESSOR UNLOADER I 61 BY CCLOWKZ'Q HYS'ATTORNEY Filed Aug. 25, 1934 Patented Dec. 24, 1935 UNITED STATES PATENT OFFICE COMPRESSOR UNLOADER Application August 25, 1934, Serial No. 741,442

4 Claims.

This invention relates to compressors, but more particularly to a compressor unl'oader adapted to unseat a compressor valve.

One object of the invention is to prevent injury to the valve plate by the lifting device.

Another object is to assure against leakage of fluid from the compressor through the unloader.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawing accompanying this specification and in which similar reference numerals refer to similar parts,

Figure l is a longitudinal "elevation, partly in section, of a compresso'requipped with an unloader constructed in accordance with the practice of the invention, and

Figure 2 is an enlarged View, in sectional elevation, of the compressor unloader.

Referring more particularly to the drawing, 25 designates, in general, a compressor'compr'ising a cylinder 2| and heads 22 and 23 which form closures for a piston chamber 23 in the cylinder.

The piston chamber 24 contains a piston 25, double acting in the present instance, for compressing fluid admitted into the ends of the piston chamber by apertures 26 opening into an inlet chamber 2? in the cylinder 2|. The fiuid compressed by the piston 25 is discharged through apertures 28 opening into a discharge chamber '29 whence such fluid may pass through a conduit 39 into a storage receiver 3|. The apertures 28 are controlled by suitable discharge valves 32 and the admission of fluid into the piston chamber is controlled by inlet valves seated in each of the apertures 26 and designated, in general, by 33.

The inlet valves, which are inserted into the apertures 29 through apertures 34 in the outer Wall of the inlet chamber 21, comprise the usual valve seat 35 and a stop plate 36 connected to the valve seat as by means of a threaded stem 31 and a nut 38. On the valve seat 35 and the stop plate 36 are seating surfaces 39 and 43, respectively, for a valve plate 4| which is adapted to reciprocate between the seats 39 and :33 for controlling a port or ports 42 in the valve seat 35. A spring 43 interposed between the valve plate 4| and the seat 49 urges the valve plate 4| in the direction of the seating surface 39.

A closure is provided for the aperture 35 in the form of a cover 44 having an aperture 45 and the inner portion 46 of which is threaded to receive a guide member 41. The inner end of the guide member 41 seats against an end wall 48 of a valve retainer 49 seated upon the valve seat 35 to hold the valve assembly fixedly in the cylinder 2|. In the skirt portion '59 of the valve retainer extending from the end wall 38 to the valve seat are ports 5 ita afford communication between the inlet chamber 2i and the interior of the valve retainer, and on the outer surface of the end Wall 5 38 1s a stem 52 which extends into a bore 53 in the guide member 4'? for maintaining the valve retainer substantially coaxial with the aperture 3% and, therefore, with the aperture 26.

The valve retainer encases a valve lifting de- 10 vice 55 comprising a plate 55 and a stem 56 which extends slidably into a bore 51 in the end wall and the stem 52 of the valve retainer. The plate 55 carries fingers 58 which extend into the ports 52 of the valve seat to a point closely adjacent 15 the seating surface 39 and are of such length that they will be out of contact with the valve plate 4| in the retracted position of the lifting device.

The lifting device is normally held out of engagement with the valve plate 31 by a spring 59 interposed between the valve seat 35 and the plate 55.

In the form of the invention illustrated the lifting device 54 is adapted to be actuated manually, To this end an actuator 69, consisting of a rod, is disposed within the guide member 41 for actuating the lifting device 54 to lift the valve plate 41 from the'seat 39. The outer end of the actuator 53 carries gripping portions 3| for'rotating the actuator 60 and near the other end of the actuator '69 is a threaded portion 52 which engages threads 63 in the guide member 41. A collar 54 adjacent the threaded portion 62, and which may be an integral portion of the actuator 99, serves as a seat for a spring 65 acting against the stem 53 of the lifting device 54,

The spring 55 is of higher scale than the spring 53 so that when the actuator 69 is being manipulated to lift the valve plate 4| the movement thereof will be positively transmitted through the spring 55 and the lifting device 54 to the Valve plate.

Means are provided for definitely limiting the degree of movement of the actuator in order that complete compression of the spring 65 and, therefore, the establishment of a rigid path between the actuator 59 and the valve plate 4| may be avoided. The means serving this purpose are in the form of seating surfaces 56 and 61 on the free end of the stem 52 and in the bottom of the bore 53, respectively, for the ends of the flange 63. The seating surfaces 56 and 61 are so spaced with respect to each other that the distance which the flange 63 may travel will be only of sufficient extent to allow the spring 65 to be compressed to a degree that Will assure lifting of the valve plate 4| from the seating surface 39 without, however, making it possible to fully compress the spring 59 and thus cause the fingers 58 to puncture or distort the valve plate.

In addition to the function described the flange 64 also serves to prevent leakage of fluid through the guide member 41 to the exterior of the compressor. 64 accordingly constitute sealing surfaces 68 and 69 which, in the limiting positions of the actuator 60, cooperate with the surfaces 61 and 66 to effect fluid tight joints. Thus, when the actuator is shifted to a position for lifting the valve plate 4| the flange 64 bears against the surface 66 and prevents the passage of fluid through the guide member 41, and in the fully retracted position of the actuator the flange bears against the seating surface 67 and prevents such fluid as may enter the bore 53 from passing through the guide member to the atmosphere. The guide member 41 may, however, be additionally sealed on its periphery by a suitable packing device in the cover. 44 and by a packing device H disposed'in its outer end to prevent leakage of fluid'along the actuator 60. V

During'the normal operation of the compressor, the actuator 66 occupies a position in which the flange 64 seats against the seating surface 61 and cooperates therewith to prevent leakage of fluid through the guide member 41. The springs 65 and 59 are then extended and the lifting device 54 occupies a position in which the ends of the fingers 58 are out of contact with the valve plate 4| which may reciprocate freely for controlling the flow of fluid through the aperture 26. Whenever it is desired to effect unloading of the compressor the actuator 60 is rotated to move in the direction of the seating surface 65. This movement of the actuator compresses the springs 65 and 59 and advances the fingers 58 against the valve plate 4|. Continued movement of the actuator 6B in the same "direction causes the valve plate to be fully unseated and carries the flange 64 against the seat 66 to prevent leakage of fluid from the inlet passage 21 into the bore 53.

I claim: 7 a

1. A compressor unloader, comprising a valve seat having a port, a valve plate for controlling the port, a valve lifting device for lifting the valve from the seat, an actuator for the lifting device,

The outer and inner ends of the flange guide members having seating surfaces thereon, a spring for transmitting the movement of the actuator to the lifting device, means on the actuator adapted to engage the seating surfaces for limiting the movement of the actuator, thereby preventing leakage of fluid through the guide members, and preventing the complete compression of the spring and the establishment of a rigid path between the actuator and the valve plate.

2. A compressor unloader, comprising a valve seat having a port, a valve plate for controlling the port, a valve lifting device for lifting the valve from the seat, an actuator for the lifting device, guide members having seating surfaces thereon, a spring for transmitting the movement of the actuator to the lifting device, a lateral projection on the actuator adapted to engage the seating surfaces to prevent leakage of fluid through the guide members and to limit the movement of the actuator, thereby preventing the complete compression of the spring and the establishment device having seating surfaces thereon, a spring for transmitting the movement of the actuator to the lifting device, ,a flange on the actuator adapted to engage the seating surfaces to limit the movement of the actuator for preventing complete compression of the spring and to prevent leakage of fluid through the guide members.

4. A compressor unloader, comprising a valve seat having a port, a valve plate for'controlling the port, a valve lifting device for lifting the valve from the seat, an actuator for the lifting device, guide members for the actuator and the lifting device having seating surfaces thereon, a spring for transmitting the movement of the actuator to the lifting device, a flange on the actuator adapted to engage the seating surfaces to limit the movement of the actuator for preventing complete compression of the springand to prevent leakage of fluid through the guide members, and a spring to normally hold the lifting device disengaged from the valve plate.

RAYMOND C. MCALLISTER. 

